There does not appear to be any reason to think that Frances Williamson was first married to Robert Bird or John Bryant. I find no record/connection, in The Parish Register of Christ Church, Middlesex Co., VA.
Frances was born in 1682, as WILLIAMSON and married in 1704, as WILLIAMSON.
My research shows the following:
21 Dec 1682, Middlesex Co., VA: ffrances the Daughter of Richard and Katherine Williamson was borne the 21th of Decemb 1682.
(The Parish Register of Christ Church, Middlesex County, Va., from 1653-1801, National Society of the Colonial Dames of America in the Commonwealth of Virginia, Rev. Silas Emmett Lucas, Jr., 1988, p 19)
16 Feb 1704, Middlesex Co., VA: John Alding & ffrances Williamson ye 16th ffebruary 1704. (ibid, p 79)
01 Apr 1727, Middlesex Co., VA: John Alding dyed April ye I. & was buried April ye 3. 1727. (ibid, p 184)